1. Field of the Invention
The present invention generally relates to wireless communication networks. In particular, the present invention relates to wireless packet data networks.
2. Background
Wireless communications that involve transmitting Internet based data over cellular networks have become more popular. As a result, the efficient scheduling of data transmission to multiple cellular mobile stations has become critical. Several techniques have been used to schedule data transmissions to cellular mobile stations. In a round robin technique, data is transmitted to each mobile station that has data in a queue until each mobile station has received a transmission. After all of the mobile stations have received a data transmission, this process is repeated. In another technique, data is transmitted to the mobile station based on the size of the backlog of data in a queue. In still another known technique, data is transmitted to the mobile station based on the data arrival instants for the mobile station.
Although the techniques discussed above are useful in providing efficient scheduling of data transmission to cellular mobile stations, there remains a need to provide the same type of Grade of Service (GoS) in wireless communication networks as is enjoyed in conventional pricing of wire line data access. Furthermore, the need to maintain proper Quality of Service (QoS) in voice and data transmission systems is of significant importance.
In wire line networks, pricing levels depend on bandwidth. For example, DSL subscribers pay more than dial-up Internet subscribers to get a higher GoS, QoS or bandwidth. Therefore, in the wire line model it is simple to proper service to users since users are easily differentiated by way of their connection type to the Internet.
The differentiated service model is equally applicable to wireless data networks. For example, it would be advantageous to create three classes of users “A”, “B”, and “C”, such that the “A” users are offered higher throughputs than “B” users, who in turn are offered higher throughputs than “C” users. In this example, each GoS class could be characterized by a “guaranteed” minimum throughput and a maximum “allowable” throughput. To upgrade one would need to pay more and then would be able to enjoy a higher minimum rate and a higher maximum rate. In order to offer these grades of service, guarantees are essential and these promises need to be kept. The lower limit is a promise to the customer, and the higher limit is crucial for making business sense. This example is akin to the pricing based on comfort that exists in airline travel: first class travelers pay more than business class travelers, and business class travelers pay more than economy class travelers.
An alternative scenario is one in which a GoS is characterized by a target throughput. The need for target throughputs arises in situations where there is a certain amount of data to be transmitted every so often without the possibility of much buffering. This is a common occurrence with delay and/or jitter sensitive services such as Voice over Internet Protocol (VoIP) and streaming audio and video. Consequently, provisioning a higher throughput is a waste of resources when there is little or no data to transmit. On the other hand, lower throughput could result in loss of data and reduced service quality. This motivates the need for methods to offer a target throughput.
Unlike dial-up and DSL, the wireless channel is a shared medium, and varies with time. Furthermore, data rates are widely disparate depending on a user's position in the cell. This problem is more acute in Code Division Multiple Access (CDMA) than in Time Division Multiple Access (TDMA) due to its interference-limited nature. Therefore, provisioning of GoS in wireless networks is an interesting technical challenge.